The need to protect sensitive electronic circuits, components or equipment against unauthorized access is well known. For example, electronic circuits, components and systems used in military weapons or other fielded military equipment can contain classified structures or data that needs to be protected against unauthorized access. Notably, the strategic, tactical or operational value of the classified structures or data that may be compromised by such unauthorized access is unquantifiable. Also, the ability to protect such sensitive electronic circuits, component or systems against unauthorized access is weakened if the sensitive electronic circuits, components or systems are not under domestic control (e.g., foreign military sales of classified weapon systems).
Similarly, electronic circuits, components or systems used for civilian applications can contain sensitive, proprietary information that needs to be protected against unauthorized access. For example, financial institutions and corporations use computerized systems to protect sensitive information (e.g., personal data, customer data, financial data, financial transaction authorization codes, authentication procedures, security passwords, etc.). Such sensitive information may be stored in alterable semiconductor memory devices (e.g., flash memory device, EPROM, EEPROM, PROM, RAM, DRAM, etc.) or memory components of integrated circuits. Any compromise in the security of the sensitive data contained in such memory devices or integrated circuits can result in significant tangible and intangible losses to the financial institutions and corporations involved, such as, for example, financial losses, losses due to fraudulent transactions, business losses, losses due to compromised customer lists and financial data, losses of institutional or corporate integrity, losses of commercial confidence, and losses due to adverse publicity. Thus, electronic circuits, components or systems containing sensitive information used for civilian applications also need to be protected against unauthorized access.
One technique for protecting sensitive hardware and software devices is discussed in commonly-assigned U.S. Pat. No. 5,877,093 to Heffner et al., entitled “Process For Coating An Integrated Circuit Device With A Molten Spray.” Heffner et al. disclose forming a primer coating and an opaque coating on an integrated circuit or multi-chip module. A primer coating composition is applied to a surface of the integrated circuit device or multi-chip module. An opaque coating composition is then applied over the primer coating to form an opaque coating that overlies the active circuitry on the surface, in order to prevent optical- and radiation-based inspection and reverse engineering of the active circuitry. Other related coating techniques for protecting sensitive hardware and software devices are discussed in commonly-assigned U.S. Pat. No. 6,287,985 to Heffner et al., entitled “Process For Applying A Molten Droplet Coating For Integrated Circuits,” and commonly-assigned U.S. Pat. No. 6,319,740 to Heffner et al., entitled “Multilayer Protective Coating For Integrated Circuits And Multi-chip Modules And Method Of Applying Same.” Notably, such protective coatings for sensitive hardware and software devices are referred to as anti-tamper coatings.
A significant problem with existing anti-tamper coating techniques is that the coatings are highly complicated structures, which are designed to thwart an intruder's physical or electronic attempts to access the active circuitry underneath (e.g., by drilling through or removing the coating, and/or optically or electronically detecting the structure of the active circuitry underneath). Consequently, it is a very complicated, time consuming, and expensive process to evaluate the quality of an anti-tamper coating on a part, or test and evaluate the performance of such an anti-tamper coated part. For example, if a number of anti-tamper coated parts are produced for a classified, government application, then these parts can be shipped to an authorized government facility for specialized evaluation and testing. However, the specialized testing and shipping of these parts are very time consuming and expensive processes, and the tested parts are typically destroyed or made useless as a result. As another example, each anti-tamper coated part can be tested individually to determine if the coating has damaged that part. Again, these tests are very time consuming and performed with expensive, specialized equipment, and the tested parts are typically destroyed or made useless as a result. Therefore, it would be advantageous to provide an improved system and method for non-destructively testing and evaluating anti-tamper coatings on sensitive electronic parts, which use inexpensive processes that take relatively little time to perform. As such, one non-destructive technique that can be used to determine the performance of the constituent elements in an anti-tamper coating material and thus the performance of the anti-tamper coating itself, is to measure the thickness and uniformity of the anti-tamper coating on the part. As described in detail below, the present invention provides such an improved system and method, which can be used to non-destructively determine the thickness and/or uniformity of an anti-tamper coating material on a sensitive electronic part.